Field
The described technology generally relates to a pixel circuit that is included in an organic light-emitting diode (OLED) display.
Description of the Related Technology
OLED displays are manufactured as a matrix of individual pixel circuits. Each pixel circuit includes an OLED that defines a pixel of a particular color. In order to have grayscales which define a range of color in an OLED, it is generally necessary to have a linear relationship of luminance to current density in the OLED over a wide area of each pixel.
Generally, to have this relationship over a wide area of the pixel, it is necessary to enlarge an operation range of the OLED. To achieve this purpose, lowering a slope of a drain current Id graph in a saturation area may be used.
In general, a drain current in a saturation area of a transistor is represented by Equation 1.
                              I          d                =                              1            2                    ⁢                      W            L                    ⁢                      μ            n                    ⁢                                                    C                ox                            ⁡                              (                                                      V                    GS                                    -                                      V                    TH                                                  )                                      2                                              (                  Equation          ⁢                                          ⁢          1                )            
Typically, drain currents have been reduced by increasing the channel length L of a driving transistor, largely providing a reasonable range of color in the OLED.
However, when a resolution of a display device increases, a size of a pixel within the display device decreases and thus because the space a pixel circuit can be disposed within decreases, it is difficult to largely secure an operation range of the OLED using a method of increasing a channel length of a driving transistor.
Further, because a channel length cannot be increased with a real RGB method, another technique to lower a slope of a current curved line should be used.
The above information is designed to assist in understanding the disclosed technology and therefore it may contain information that does constitute prior art.